The present invention relates to an arrangement for producing a spun thread from a staple fiber strand, comprising a drafting unit having a delivery roller pair, also comprising an airjet assembly arranged downstream thereof, which airjet assembly comprises a vortex chamber having an air evacuation channel, also comprising at least one cleaning channel, which is arranged with a suction opening to the delivery roller pair.
An arrangement of this type is prior art in European published patent application 1 207 225. In the case of this arrangement, a staple fiber strand is drafted in a drafting unit to a thin fiber strand, to which the spinning twist is then imparted in the airjet assembly. For this, the fiber strand is first fed through an entry channel of the airjet assembly into a vortex chamber, to which a fluid device is assigned for generating a vortex stream around an entry opening of a thread withdrawal channel. The front ends of the fibers held in the fiber strand are thereby initially fed into the thread withdrawal channel, while rear free fiber ends spread out, are seized by the vortex current, and are twined around the front ends already located in the entry opening of the thread withdrawal channel, that is, around the front ends already intertwined, by means of which a thread having, to a large extent, a real twist is formed.
An arrangement of this type permits high spinning speeds, while placing high demands primarily on the drafting unit arranged upstream of the airjet assembly. In particular, the especially fast rotating delivery roller pair is subject to fiber fly deposits on its peripheral surfaces. For this reason, a suction opening of a cleaning channel is operatively arranged with respect to the delivery roller pair of the known arrangement, which cleaning channel ensures that the delivery roller pair is kept clean. The above mentioned publication does not disclose to which vacuum source the cleaning channel is connected, but it can be seen from the patent drawings that different vacuum sources are clearly provided for the air evacuation channel and the cleaning channel.
It is an object of the present invention to provide a particularly simple design for an arrangement of the above mentioned type, and furthermore to intensify the cleaning process when required.
This object has been achieved in that the cleaning channel is connected to the air evacuation channel via a mouthpiece, and that in the area of the mouthpiece, a compressed air opening of an injector channel for increasing the low pressure in the air evacuation channel, when required, is provided.
Because the cleaning channel is connected to the air evacuation channel with a mouthpiece, a joint fan for the waste air sucked out of the vortex chamber and for the cleaning of the delivery roller pair can be used, which leads to a significantly reduced complexity in the manufacturing process in comparison to the prior art. Because a compressed air opening of an injector channel for increasing the low pressure in the air evacuation channel when required is provided in the area of the mouthpiece, the low pressure can be temporarily increased, and even almost doubled, for the purposes of intensifying the cleaning process. This is possible without increasing the capacity of the fan. The injector channel can retroact with maximum effect up to the suction opening, as it runs in with its compressed air opening at a particularly effective point. The suction action can thus be increased for periodical cleaning by periodically activating the injector channel when required, particularly in the case of an interruption in the spinning process and a subsequent piecing process. The increased effect is particularly high when the cleaning channel extends straight-lined between its suction opening and its mouthpiece, and when it preferably measures a maximum length of 20 mm.
In an advantageous embodiment of the present invention, it is provided that the airjet assembly, together with the cleaning channel, can be swivelled in relation to the delivery roller pair in such a way that the suction opening can be positioned to the area of the wedge-shaped gap formed by the delivery roller pair. After an interruption in the spinning process, when a thin fiber strand is again fed through the drafting unit to the airjet assembly, an initially inhomogenous fiber stream is deflected from its normal transport direction, namely through the suction opening of the cleaning channel. The fiber strand is initially removed as waste, until a homogenous fiber stream is achieved, whereafter the increase in outgoing air effected by the injector channel can be cut off again. The swiveling capacity permits the suction opening of the cleaning channel to be directed not only against a peripheral surface of the delivery roller pair, but rather directly into the wedge-shaped gap of the delivery roller pair, from which wedge-shaped gap the thin fiber strand is supplied.
It is known from European published patent application 0 807 699 that in connection with a piecing process, a fed fiber strand is temporarily deflected, which in this case, however, occurs via an additional suction tube, which is located between the delivery roller pair and the airjet assembly.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description of an arrangement shown both enlarged and in schematic cross-sectional form.